Wearable LED pixel with my own shady charger.

It's always nice to visit older projects and see how I did things in the past. This device dates back to when blue LEDs were first available. Up to that point all LEDs had been in the range of infrared, red, orange, yellow and a dull apple-green, so the new era of blue and white LEDs was quite special. The first blue LEDs cost £10 each making them about 200 times the cost of a normal LED.
Since it was a new style of light source and was capable of giving out a deep and psychedelic blue light that had not been achievable at low level with small tungsten lamps, I decided to make a small battery pack system that let me wear a blue LED in my hard hat at work or in a jacket or sweatshirt at the weekend. It got a lot of attention at the time because in a world where blue LEDs hadn't existed before it created a very odd visual effect.
The charger was deliberately very simple and used a low trickle current to charge the battery pack. Since the normal charging current of these packs is very low (memory backup batteries) it suited a very basic resistive dropper directly powered from the mains. This also meant that the exposed pins on the charger could give a shock, but not a dangerous one. That little twist of danger was part of the fun of it.
These days I might consider using a simple lithium ion battery with a zener for voltage capping and maybe a USB or solar powered charger.

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